The present invention pertains to a timepiece which is receptive of a broadcast time signal for correcting a time error on the basis of the received time signal. More particularly, the present invention pertains to a timepiece receptive of a broadcast time signal for correcting a time error and having circuitry for reducing the consumption of power.
Japan has recently begun broadcasting, on a trial basis, a time code signal which is superposed on a standard frequency long radio wave. This time code signal is being broadcast under the control of the Ministry of Posts and Telecommunications, and is effective for correcting a time error in timepieces that are receptive of the time signal. The broadcast time signal includes correct time data indicative of hours and minutes of the days accumulated since January 1 , and the data are transmitted in series in the form of a binary code having one frame per minute.
More specifically, the time signal is broadcast having one bit formed by a 1-Hz square pulse. The binary values of "1" and "0" are represented by pulse widths of 500 ms and 800 ms, respectively. Position markers are represented by 200 ms pulses, and the carrier wave has a frequency of 40 KHz.
In order to make use of the broadcast time signal for correcting a time error, timepieces are being provided with a receiving circuit. The receiving circuit is supplied power each day at a predetermined time and for a constant time interval. Thus, the receiving circuit can receive the broadcast time signal having correct time data so as to adjust for discrepancies of time in the timepiece.
However, since the time signal is received by the timepiece every day at a predetermined time, the timepiece is adjusted every day. The timepiece is adjusted in spite of the fact that daily time adjustment may be unnecessary if the precision of the particular timepiece is high. Therefore, a problem exists in that power may be unnecessarily consumed each time the timepiece receives the time code signal.